This invention relates in general to jack designs and in particular to lifting jacks employing a pair of climbing pins.
Lifting jacks of the type employing climbing pins have been known in the art for many years. Early patents disclosing such structures date back as far as the early 1900's, and while various improvements have been made over the years, many aspects of this type of structure which employs a pair of runners, have remained substantially unchanged over the years. The design concept includes a standard with a series of spaced apertures and a pair of climbing pins which alternately fit into these apertures as their corresponding runners move along the standard in a step-by-step fashion which is controlled by a handle (lever) member. A reversing mechanism enables the runners to be moved along the standard, intermittently in either direction.
The following listed patents are generally typical of the above style of lifting jack.
______________________________________ Pat. No. Patentee Issue Date ______________________________________ 1,307,968 Harrah 6/24/19 1,374,653 Harrah 4/12/21 Des. 248,460 Dunn et al. 7/11/78 1,482,846 Harrah 2/05/24 ______________________________________
Harrah ('968) discloses a lifting jack designed and arranged so that the lowering action as well as the lifting movement is effected in a step-by-step manner. To accomplish this objective, the disclosed structure includes a standard having a plurality of perforations and a pair of runners movable on the standard. Each of the runners is provided with a spring-actuated pin adapted to be projected into a corresponding perforation. An operating lever mechanism causes the runners to alternately move along the standard and a reversing plate enables movement of the runners in the opposite direction.
Harrah ('653) discloses a lifting jack which is intended to be an improvement over U.S. Pat. No. 1,307,968, yet is quite similar in that its structure includes a standard formed with holes and a pair of runners which are movable along the standard. Each of these runners is equipped with a spring-actuated pin for alternately entering the holes of the standard in order to constitute a fixed stop while the other runner is advancing. A lever mechanism enables movement of the runners along the standard. This particular patent reference is intended to be an improvement to the earlier patent by enhancing the strength and efficiency of the device. A related improvement is that the nose or step of the jack is allowed to approach quite closely to ground and thus enables the particular jack disclosed to get under loads which are disposed very low to the ground level.
Dunn et al. discloses a jack which employs the dual-runner, dual-pin concept for advancing the nose of the jack along a perforated standard. Although this particular patent is a design patent, the general external appearance of the component parts may provide the closest reference to the present invention.
Harrah ('846) discloses a pole pusher and while some of this structure may be unrelated to the present invention, the mechanism which accounts for movement of cylinder 24 relative to base 22 is the same as that disclosed in U.S. Pat. No. 1,374,653. This mechanism employs a dual-pin concept, the pins being insertable into holes in the standard, a handle to move the runners along the standard in a step-by-step manner, and a reversing mechanism for changing the direction of movement of the runners relative to the standard.
One of the improvements over the general state of the art provided by an early patent (U.S. Pat. No. 1,307,968) was to permit the lowering action to be accomplished in a step-by-step manner. A later patent (U.S. Pat. No. 1,374,653) provided the improvements of greater strength and efficiency, a novel manner of mounting the hand lever and the relative configurations and positions of the runners. By revising the runner configurations, the nose (step) of the jack is placed close to the ground and is better able to get beneath low loads.
While there may be other improvements possible as new and varied uses are found for this type of lifting jack, one type of improvement provided by the present invention is a revision in the style and configuration of the various component parts which are assembled together in order to provide greater strength and durability with a more efficient method of fabrication, and lower cost.
Since the patentability of an article of manufacture is based upon its novelty and utility, it is not sufficient that a claimed article merely be different from prior art articles. The claimed article must also have utility, and in the case of related articles, it must be novel and a useful improvement over the prior art. Usefulness (utility) has been found in inventions which provide improvements in safety, are more convenient to use, are more efficient, are more durable and less expensive. Consequently, when a component part of a larger apparatus is changed and this change is claimed as part of a patent application, the change must satisfy one of the above criteria in order to provide utility and thus be classified as "useful." When a component part is restyled so that it is less expensive to manufacture, or stronger, or easier to assemble or use, utility for the claimed invention exists even though the external appearance of the component part may seem similar to a corresponding component part in a prior art apparatus.
The disclosed and claimed lifting jack of the present invention incorporates a number of component parts which represent improvements over corresponding component parts of the above-listed patent references. In certain instances, the component parts may be stampings, and in other instances they may be castings. In each instance where a part has been redesigned to provide additional utility and is an improvement to earlier designs, its specifics as to manufacturing and reconfiguration are described in detail.